The invention relates to bowl-mill gearing having
an annular gear case,
a receiving plate, which can be driven about a vertical mill axis, for a grinding bowl,
a thrust bearing to support the receiving plate on the gear case,
an epicyclic gear through which the receiving plate can be driven, and
an intermediate gear with a driving shaft and a driven shaft which is arranged coaxially with the receiving plate and is coupled to the sun wheel of the epicyclic gear and which carries the driven wheel of the intermediate gear.
Bowl-mill gearing of this type which is known from DE-PS 31 45 655 goes back to the year 1981. Before the introduction of such bowl-mill gearing with a built-in epicyclic gear, the most widespread type of construction for gearing for the drive of bowl mill crushers was a two-stage parallel-shaft gear with an intermediate gear in the form of a bevel gear. The bevel gear renders possible the use of a driving motor installed at ground level with a horizontal shaft. The vertical driven shaft of the parallel-shaft gear drives the receiving plate with the grinding bowl mounted thereon. The receiving plate transmits the very great axial grinding forces to a pressure plate through pivoted pads of a thrust bearing. The pressure plate, which is secured at the top to the gear case, likewise of annular construction at least below the receiving plate, then transmits the axial grinding forces through the gear case to the bed plate of the bowl mill crusher. Because of the gear wheels of the two gear stages of the parallel-shaft gear, its gear case has to be cut open laterally at least over about a fifth of its circumference. Because of the cut-away gear case, the large axial forces which act on the receiving plate cannot be distributed symmetrically and drawn off into the bed plate. In order that a more or less satisfactory distribution of load over the pivoted pads of the thrust bearing may nevertheless be achieved, the pressure plate of the gear case must be made very stiff and very heavy.
In the bowl-mill gearing of the type mentioned at the beginning, which is known from said DE-PS 31 45 655, the problem of the uniform transmission of the axial load is ideally solved by means of the epicyclic gear since the axial forces are transmitted to the bed plate through the completely symmetrical, annular gear case. But this known bowl mill gearing also comprises a bevel gear as an intermediate gear in order that a driving motor disposed at ground level with a horizontal shaft may be able to be used. The bevel gear is an angular gear, the driving shaft of which likewise requires a cut-out in the annular case but this is very small in comparison with the cut-out necessary with the known parallel-shaft gear and only weakens the wall of the gear case to a negligible extent. The loading capacity of bevel gears is limited, however, for which reason an effort is made to avoid these.
DE-PS 32 40 222 shows such a possibility of avoidance in the form of a bowl mill crusher which likewise comprises an epicyclic gear but in which the external wheel of the epicyclic gear is not supported on an annular gear case which rests on the bed plate but is suspended, via an annular flange projecting outwards, on a frame resting on the bed. This construction of the bowl mill crusher renders possible the use of a driving motor with a vertical shaft, which motor is disposed below the epicyclic gear coaxially with this and may be provided with its own reduction gear mounted directly on it. As a result, a bevel gear and a cut-open case with the associated disadvantages are admittedly eliminated but at the expense of the arrangement of the whole bowl mill crusher at ground level since a basement is necessary for the driving motor. Such a basement is not possible in all cases, requires a special construction of the bowl mill crusher and so involves additional costs.
It is the object of the invention to eliminate a bevel gear as an intermediate gear in bowl-mill gearing of the type mentioned at the beginning without it being necessary to provide a basement below the bowl mill gearing for the driving motor and without the transmission of axial load being appreciably impaired.